The objective of this project is to study the clinical applications of a new viewer for tomographic scans which allows the physician to examine multiple scan sections simultaneously in the proper relationship in all three dimensions. Test images shown on a prototype device clearly show stereopsis and parallax depth cues characteristic of a real three dimensional object. We are evaluating this device using x-ray CT and B-scan ultrasound data, also radiation therapy dose profiles, to determine the extent to which these data are more comprehensible when viewed in 3-D. Our primary objective in this reporting period is to complete the construction and checkout of a viewing device suitable for evaluation in a clinical environment. A second objective added midway through the current period is to evaluate the use of the viewing as a means of guiding the stereotaxic surgical frame developed by Dr. R. A. Brown for invasive procedures in the brain. To accomplish this objective it will be necessary to attach the completed viewer to a small portable computer system so the unit may be moved to and from the neurosurgery operating suite.